CHANGES IN DIATOM ASSEMBLAGES IN LAKE C2 (ELLESMERE ISLAND, ARCTIC CANADA) - RESPONSE TO BASIN ISOLATION FROM THE SEA AND TO OTHER ENVIRONMENTAL-CHANGES

Diatoms preserved in the sediments of Lake C2 (82 degrees 50'N, 76 deg rees 00'W), a high arctic meromictic lake, track changes in the lake's salinity which have occurred as the basin was isolated from the sea. An assemblage dominated by marine taxa, such as Chaetoceros species, N itzschia cylindrus and Diploneis spp., was replaced by a Cyclotella ku etzingiana var. planetophora dominated freshwater flora. A brief brack ish period separates the two assemblages. Relatively little floristic change occurred within either the marine or freshwater periods, indica ting rather stable environmental conditions, except that rheophilous d iatoms fluctuated in relative abundance during the lacustrine phase, p erhaps tracking past changes in discharge from inflowing streams. Thes e may reflect periods of warmer, wetter environmental conditions.